Oscillators hermetically enclose the vibrating region of piezoelectric resonators, which are configured to effect piezoelectrical vibration, examples including a crystal oscillator.
Crystal oscillators each include a package defined by a base of a ceramic material in the form of a box and a single plate lid of a metallic material. In the internal space of the package, a piezoelectric resonator and an IC chip are held by and bonded to the base. The bonding of the base and the lid hermetically encloses the piezoelectric resonator and the IC chip in the internal space of the package (see, for example, Patent Document 1).
A crystal oscillator described in Patent Document 1 uses a base that includes two box bodies of ceramic materials that are layered one on top of one another by integral burning. One of the box bodies of the base internally includes a piezoelectric resonator, while the other box body internally includes an IC chip. The base includes, on its rear surface (other principal surface), external terminals to be electrically coupled to an external circuit board, and inspection terminals to measure and inspect the properties of the crystal resonator. The external terminals and the inspection terminals are formed along the outer periphery of the other principal surface.